The present invention relates generally to measuring equipment and more particularly to measuring equipment of the kind that includes a plurality of sensors which are each adapted to sense a measurement magnitude, and which further include a xe2x80x9cmeasuring cardxe2x80x9d to which said sensors are connected, and a computer unit to which said measuring card is connected.
The invention may be based on providing said measuring card with two mutually opposite electrical contact means, of which a first is adapted for coaction with a corresponding electrical contact means belonging to a computer unit, and the other is adapted for coaction with a corresponding sensor-mounted electrical contact means and thereby create conditions to form a simple and light measuring equipment that can be brought along by a mechanic or repairman in order to evaluate an imbalance or balance of a rotating machine or shaft on site.
The invention also includes the embodiment where a rotating machine can be continuously controlled with regards to balance or imbalance by including the measuring card in a controlling unit and/or process-regulating unit and to thereby integrate the measuring equipment with the unit.
The inventive measuring equipment is based on adapting a first sensor to sense a prevailing frequency generated by an object to be measured, while a second sensor is adapted to sense prevailing tacho-pulses generated by the object being measured.
More particularly, the measured object includes a rotating object, such as a shaft or axle, and the measuring equipment functions to enable an evaluation of different types of imbalance in the rotary movement of the rotating object from measurements received from the rotation of the object, such as a result of cracks in the object, rotational asymmetric imbalances, varying degrees of imperviousness in the material from which the object is made, and so on.
Various designs and configurations of measuring equipment of the aforedescribed kind are known to the art.
For instance, there is known to the art measuring equipment that includes one or more sensors for sensing one or more temperatures with the aid of a measuring card and a computer unit to this end.
One such measuring card is marketed in Sweden under the designation Ines DMM and DAQ I218 by PC Card Distribution Skandinavien AB, Solna, Sweden.
Measuring equipment of this kind thus enables one or more prevailing or current temperatures to be presented on the screen of the computer unit.
It is also known to configure a measuring card of this kind as a digital multimeter having a determined digital resolution or a 16-channel data collecting system.
In this regard, there is also provided a data collection of analogue levels with 24-bit resolution.
The measuring cards are comprised of an A/D converter and a digital electronic unit, among other things.
It is also known to enter into the computer unit information relating to the front surface of a known measuring unit and to present relevant, or current, values such as temperature values, within the area of the presentation surface of said measuring unit.
Patent Publication GB-A-2 177 509 teaches a method and an arrangement for detecting axial cracks in a rotor of rotary machines, by sensing vibration frequencies with the aid of sensors (38, 40) and correlating the frequency of the vibrations with the angular position of the rotor with the aid of a sensor (37).
Data relating to angular velocity is obtained through the medium of a cogwheel (35) and a magnetic sensor (37), said cogwheel (35) having ten equidistant teeth and therewith producing a detectable tacho-pulse at each 36th degree of rotation.
Patent Publication U.S. Pat. No. 5,610,339 teaches a method of evaluating and anticipating the conditions of a machine that includes at least one rotary element, with the aid of a vibration sensor (12) and a tacho-pulse sensor (14).
When taking into consideration the technical deliberations that a person skilled in this particular art must make in order to provide a solution to one or more technical problems that he/she encounters, it will be seen that on the one hand it is necessary initially to realise the measures and/or the sequence of measures that must be undertaken to this end, and on the other hand to realise which means is/are required in solving one or more of said problems. On this basis, it will be evident that the technical problems listed below are highly relevant to the development of the present invention.
It will be understood that by the term tacho-signals as used in the following description is meant the tacho-signals that are generated or formed internally in the measuring equipment and that are required for evaluation of the measuring result. These tacho-signals have a higher frequency than tacho-signal initiating pulses, abbreviated to tacho-pulses, this expression being understood as meaning tacho-signals that are formed via a tacho-pulse receiving and controlling sensor.
When considering the present state of the art as described above, it will be evident that a technical problem resides in creating with a starting point from the basic features of the known technology conditions which will enable the measuring equipment to create conditions, with the aid of simple means, so as to obtain the tacho-signals generated in internal circuits and necessary to the measuring process through the medium of signal processing and by increasing the frequency of received tacho-pulses, in addition to evaluating prevailing sound and other vibrations generated by a rotating object, such as an electric motor, a petrol-driven or diesel-driven engine, and like machines as well as driven rotating objects, such as pumps, separators and like objects.
Another technical problem is one of enabling well-defined tacho-signals to be obtained with the aid of simple means, even in respect of objects that have not been provided with means for generating a large number of tacho-pulses during one revolution of the rotating object (such as a cogwheel), but which, nevertheless, have a readily accessible rotatable surface part, such as an exposed rotatable shaft or axle.
Another technical problem resides in realising the advantages that are afforded by applying to an accessible, rotatable surface-part one or more markings, preferably only one single marking, for generating tacho-pulses, and sensing said marking/s as it passes a few, preferably one, sensor while, nevertheless, sending to the measuring equipment a far greater number of tacho-signals for calculating purposes, through the medium of internal circuitry. Another problem in this respect resides in realising the means required to this end.
Another technical problem is one of realising the significance of and the advantages afforded by enabling an electronic unit to divide the time distance between two mutually sequential tacho-pulses into a predetermined number of sub-section, each having mutually the same duration, and generating a pulse-like tacho-signal with each such sub-section.
Another technical problem is one of realising the significance of and the advantages afforded by observing that the duration of the sub-sections can be varied in response to the speed at which the object rotates.
Yet another technical problem is one of realising the significance of and the advantages afforded by selecting only a few tacho-pulses for each revolution, say one pulse per revolution, and causing the circuit-internal electronics to perform the necessary, uniform division of the time distance between the tacho-pulses.
Another technical problem is one of realising the significance of allowing the number of time divisions, and therewith the number of tacho-signals per revolution, to be sixteen or thirty-two and therewith simplify signal processing in the computer unit.
A particular technical problem resides in realising the significance of and the advantages afforded by utilising a calculated duration for each sub-section evaluated between a first tacho-pulse and a second tacho-pulse between said second tacho-pulse and a subsequent third tacho-pulse.
Still another technical problem is one of realising the significance of and the advantages afforded by evaluating a prevailing frequency during each of said sub-sections in the electronic unit associated with said measuring card.
Yet another technical problem is one of realising the significance of and the advantages afforded by evaluating prevailing sound and vibrations and entering these into the computer unit in a structured state.
A further technical problem is one of realising the significance of and the advantages afforded by adapting the computer unit so as to show on its display the front surface of a known measuring unit intended for the same purpose, and to present prevailing measurement values obtained with the measuring equipment in the region of the presentation surface of said known measuring unit.
In respect of the above application, a further technical problem resides in realising the significance of utilising two different types of sensor through the medium of a measuring card, of which one sensor is adapted to sense continuously prevailing frequencies generated by an object being measured, and the other of which is adapted to sense tacho-pulses generated by said object.
Another technical problem is one of realising the significance of and the advantages afforded by adapting circuits in said measuring card and co-ordinating said circuits such that the circuits can be co-ordinated equally on the basis of information received with respect to prevailing frequency and prevailing tacho-pulses, essentially regardless of the speed at which the object rotates and also during significantly varying rotational speeds, such as during acceleration and retardation phases of said rotation.
The present invention utilises a measuring card that includes an A/D converter and a digital electronic unit. In this regard, it will be seen that a technical problem resides in realising the significance of and the advantages afforded by coupling the analogue information relating to prevailing frequencies to the A/D converter, and by coupling information relating to the time positions of prevailing tacho-signals directly to the electronic unit.
With the intention of solving one or more of the aforesaid technical problems, the present invention takes as its starting point measuring equipment of the kind defined in the introduction.
According to the invention, at least one of the sensors shall be adapted to sense continuously the prevailing, or current, frequency of an object being measured, and at least one sensor will be adapted to sense tacho-pulses of an object being measured, and the circuitry in a measuring card will be adapted to evaluate prevailing sound and vibrations generated by the rotating object, on the basis of information received concerning prevailing frequency and prevailing tacho-pulses. By prevailing is meant currently occurring.
It is particularly proposed in accordance with the present invention that the electronic unit shall be adapted to divide the time distance between two mutually sequential tacho-pulses into a predetermined number of sub-sections and to generate a tacho-signal at each sub-section, through the medium of calculating circuits.
In accordance with preferred embodiments, the sub-sections are given equal duration in time, and the duration of each sub-section evaluated between a first tacho-pulse and a second tacho-pulse shall be utilised within the time distance between said second tacho-pulse and a following third tacho-pulse.
This creates conditions for allowing a prevailing frequency section to be evaluated in said electronic unit during each of said sub-sections, said electronic unit being conveniently adapted to evaluate prevailing sound and vibrations by frequency analysis, and entering said sound and vibrations into the computer unit.
According to preferred embodiments that lie within the scope of the inventive concept, the present invention also utilises a measuring card that includes an A/D converter and a digital electronic unit. Continuous analogue information relating to prevailing frequency is applied to the A/D converter, and information relating to prevailing tacho-pulses is applied to the electronic unit.
In accordance with the invention, the computer unit is adapted to show on its display unit the front surface of a known measuring unit and to present prevailing measuring values in the region of the presentation area of the known measuring unit, said known unit being adapted for the same purpose.
Those advantages that are primarily characteristic of inventive measuring equipment reside in the provision of conditions which enable prevailing sound and vibrations generated by a rotating object to be readily evaluated with the aid of two different types of sensors, both of which are connected directly to a measuring card.
The measuring card may have the advantage of containing all measuring electronics for sensor current supply, and a large number of sensors having integrated electronic circuitry can be coupled to the measuring card.
Circuits embodied in the measuring card can be used to evaluate prevailing sound and vibrations generated by the rotating object.
A particular advantage afforded by the invention is that sensed tacho-pulses are chosen for each revolution and the time distance between sequential tacho-pulses is divided electronically, so as to generate internally of the measuring equipment tacho-signals whose frequencies are higher than the frequencies of the tacho-pulses.
The primary characteristic features of inventive measuring equipment are set forth in the characterising clause of Claim 1.